Magnetic hard disk drives (HDD) are the most widely used storage devices in the data storage industry today. The HDD uses magnetic heads that fly over a magnetic disk and read and write from and to the magnetic disk. In order for the head to fly over the disk in a predictable and stable manner, the head is incorporated in a slider body that has an air-bearing surface (ABS) facing the disk. With the appropriate ABS design, the slider can be flown very close to the disk. As devices that incorporate HDDs become smaller and smaller, the push for reducing the height at which the heads fly above the disk (fly height) is continuous. As fly heights decrease, the need for stability in their control, so as to avoid crashing into the disk, is ever increasing.
The sliders have aerodynamic features or “wings” on their ABS to allow them to fly at the appropriate height. To achieve a very low fly height without crashing, it is critical that the ABS structure satisfied design requirements with tight tolerances. Several techniques have been used to produce such an ABS, including mechanical machining, ion milling and reactive ion etching. For the more advanced ABS design, there are steps on the ABS that are less than 1 micrometer deep. Consequently, the required tolerance is much tighter than mechanical machining can deliver. Ion milling has been the choice of the process for this type of step. The technical challenge to produce such a step is to have uniformity of depth across the slider wafer.